a) Field of the Invention
The invention is directed to a multibeam modulator for a particle beam. In particular, the invention is directed to a multibeam modulator which generates a plurality of individual beams from a particle beam. The particle beam illuminates the multibeam modulator at least partially over its surface. The multibeam modulator comprises a plurality of aperture groups, each aperture group having a plurality of aperture row groups. The totality of all aperture rows defines a matrix of m×n cells, where m cells form a row and k openings are formed in each row.
b) Description of the Related Art
The invention is further directed to the use of a multibeam modulator for maskless structuring of a substrate. In particular, a plurality of individual beams are generated by the invention in that a particle beam illuminates the multibeam modulator at least partially over its surface. A plurality of aperture groups are formed in the multibeam modulator, each aperture group having a plurality of aperture row groups. The totality of all aperture rows defines a matrix of m×n cells, where m cells form a row and k openings are formed in each row.
U.S. Pat. No. 4,153,843 discloses an exposure system with a plurality of beams. A two-dimensional array with a plurality of openings is provided in the beam path of an electron beam exposure system. The array is illuminated over its surface by the electron beam and is imaged in a reduced manner on a substrate. Only one individual aperture plate is provided generating the plurality of individual electron beams from the surface illumination. The individual openings are uniformly distributed over the aperture plate within a row.
U.S. Patent Application US 2003/0155534 A1 discloses a maskless exposure system for particle beams. A plurality of aperture plates which are fitted one behind the other generate a plurality of individual beams from an electron beam. The uppermost two plates and the bottom plate have openings through which the electron beam passes. Each plate has a thickness of about 100 μm and the plates have a distance from one another of 100 μm to 1 mm. An array of correction lenses is arranged between the second plate and the bottom plate in front of the final aperture plate. The density of openings within a row is constant.
U.S. Pat. No. 5,144,142 discloses a particle beam system containing an aperture plate for blanking corresponding partial beams. The individual aperture plate comprises m rows and n columns of openings which are arranged two-dimensionally on a substrate. A pair of deflecting electrodes is associated with each opening. Further, n×m-bit shift registers are provided on the substrate to supply the m pairs of deflecting electrodes with voltages corresponding to the pattern data. However, the aperture plate is formed only as an individual structural component part. Also, an inhomogeneous distribution of openings within a row is not suggested.
U.S. Pat. No. 5,369,282 discloses a particle beam system which generates a plurality of partial beams from a flat electron beam by means of an aperture plate, the partial beams being imaged on a substrate. A plurality of openings are formed in the aperture plate. The openings are homogeneously distributed over the aperture plate.
U.S. Pat. No. 5,430,304 discloses a particle beam system by which a plurality of partial beams are imaged on a substrate. There is also an aperture plate in which a plurality of switchable openings are formed. The openings are controlled by means of a corresponding quantity of shift registers. The distribution of the openings in the aperture plate is homogeneous.
The article “Programmable Aperture Plate for Maskless High-Throughput Nanolithography” by Berry et al., J. Vac. Sci. Technol. B 15(6), November/December 1997, pages 2382 to 2386, discloses a programmable aperture array comprising 3000×3000 apertures which can be electronically triggered and activated individually to monitor or control the passage of the beam. The pattern to be written is introduced into the aperture plate system as a binary signal from one side and is pushed through to the other side. The aperture plate system comprises an aperture plate with the corresponding deflecting electrodes. The openings are distributed in a correspondingly uniform fashion.
The publications cited above show multibeam modulators in the form of rows or arrays in which the triggering of each control element is carried out separately. However, because of the large quantity of leads, the number of beams operating in parallel is limited to about 1000 and enables only a moderate increase in productivity in spite of the extensive resources employed.
For this reason, it was proposed to use uniform or homogeneous array structures with n rows and m columns in which the on/off information in each row is advanced from one of the m modulator elements to the next by integrated delay elements or shift registers. The time shifting of the pixel image from column to column is correlated with a scanning movement of all beams relative to the substrate so that it is possible to use all of the n×m beams in parallel, but only new data for the n modulators of the first column need be provided in every exposure cycle. The main defect in known implementations of this principle is the limiting to one bit (on/off) per exposure cycle and row, so that mandatory dosing steps, proximity corrections, and the like can only be realized to a limited extent through the use of a plurality of arrays. Known solutions for the blanking chip require a high storage density and lack flexibility.